JP5001073B2 - Injection molding machine and molding control method - Google Patents

Description

  The present invention relates to a technique for forming a thin molded product such as a disk substrate by an inline screw type injection molding machine, and in particular, from the start of continuous automatic molding operation until the temperature control of the injection molding machine is stabilized. The present invention relates to techniques related to injection control techniques.

  In an in-line screw type injection molding machine that is arranged so that the screw can be rotated and moved forward and backward in the heating cylinder, the resin material supplied to the rear end side of the screw is used as the screw rotation and heating cylinder during the weighing process. The mixture is transferred to the front while being kneaded and plasticized by heating, and one shot of molten resin is stored on the tip side of the screw. Also, during the primary injection process of the injection process, the screw is rapidly advanced from the injection start position to the holding pressure switching position, and the molten resin is injected and filled into the cavity of the mold to maintain the injection process following the primary injection process. In the pressing step, a holding pressure is applied from the screw to the resin in the cavity through a resin called a cushion amount remaining on the tip end side of the screw.

  With such an inline screw type injection molding machine, for example, when molding a disk substrate for a DVD, the molding cycle is as short as 2.0 seconds, and the thin molded product is rapidly solidified. Thus, in the molding of the disk substrate, the primary injection process is important in the injection process, and in particular, the weight of the molded product is substantially determined in the primary injection process.

  One of the important factors in the disk substrate molding quality is the thickness of the disk substrate, and this thickness correlates with the weight of the disk substrate. FIG. 5 shows the relationship between the thickness and weight of the disk substrate, the horizontal axis represents the number of shots, and the vertical axis represents the thickness and weight. As shown in FIG. 5, there is a close correlation between the thickness and weight of the disk substrate. When the weight is large, the thickness increases, and when the weight is small, the thickness decreases. Therefore, in the molding site, in order to avoid the troublesome precision of measuring the thickness of the disk substrate, by measuring the weight of the disk substrate taken out by a robot or the like, the thickness of the disk substrate that is a molded product is measured. Good / bad judgment is performed.

  By the way, in an injection molding machine such as an inline screw type injection molding machine, when a continuous automatic molding operation is started, it is known that the temperature control of the heating cylinder is not stable until a predetermined number of shots have elapsed from the start of the operation. For this reason, the quality of the molded product does not fall within the expected range until a predetermined number of shots have elapsed from the start of operation. FIG. 6 shows the relationship between the temperature of the temperature control point (channel (CH) 5) closest to the hopper in the heating cylinder and the weight of the disk substrate that is the molded product, and the horizontal axis represents the number of shots, The axis represents the weight of the disk substrate and the temperature of CH5. In the example shown in FIG. 6, one cycle is 2.0 seconds, the initial 5 shots are discarded, and data obtained by sampling from the 6th shot to the 135th shot is shown. In FIG. Is the data for the first shot. As shown in FIG. 6, at the beginning of the start of the continuous automatic molding operation, the disk substrate tends to be lighter in spite of the same primary injection advance stroke of the screw. It can be seen that it takes about 100 shots (about 100 shots excluding discarded shots) before the weight falls within the intended range.

In addition, in an injection molding machine, it is common to think that it is discarded shots until a predetermined number of shots have elapsed from the start of operation, but in this, many wasteful shots are performed at the start of molding operation Become. Therefore, Japanese Patent Publication No. 6-81697 (Patent Document 1) and Japanese Patent No. 2990406 (Patent Document 2) are techniques for obtaining good products at an early stage by changing molding conditions at the start of molding operation. ) And so on.
Japanese Examined Patent Publication No. 6-81697 Japanese Patent No. 2990406

  By the way, in the techniques shown in Patent Document 1 and Patent Document 2, the control conditions of a plurality of items are changed step by step at the start of molding operation, and a program for performing such control and suitable control are performed. There is a problem that it is difficult to select conditions, and it is not intended to be applied to molding a disk substrate having a molding cycle as short as about 2.0 seconds.

  As described above, for example, when a disk substrate for DVD is molded, the molding cycle is as short as 2.0 seconds, and the thin molded product is rapidly solidified. Thus, the weight of the disk substrate, that is, the thickness of the disk substrate correlated with the weight is substantially determined in the primary injection process. In such disk substrate molding, since the molding cycle is short, it is very uneconomical to perform a large number of discarded shots at the start-up of the molding operation, and wasteful shots at the start-up of the molding operation are made as much as possible. It is desirable to be able to reduce this, and it is desirable to be able to achieve this with a simple control technique.

  The present invention has been made in view of the above points. The object of the present invention is to minimize wasteful shots at the start-up of a molding operation when molding a disk substrate or the like with an inline screw type injection molding machine. It is also possible to achieve this by a simple control method.

  In order to achieve the above-mentioned object, the present invention is an in-line screw type injection molding machine until a predetermined number of shots elapse after a continuous automatic molding operation is started and a plurality of discarded shots are performed, or continuous automatic molding. Until the predetermined number of shots has elapsed from the start of operation, the screw injection start position is the same, but the forward stroke of the screw in the primary injection process is changed so that the cushion amount gradually increases for each shot. Control.

  In the present invention, after the continuous automatic molding operation is started and a plurality of discarded shots are performed until the predetermined number of shots elapses or until the predetermined number of shots elapses from the start of the continuous automatic molding operation, the screw is injected. Although the starting position is the same, the forward stroke of the screw in the primary injection process is changed so that the cushion amount gradually increases for each shot. Experiments have confirmed that the weight of a disk product, for example a disk substrate, is within an expected range at an early stage when such a cushion amount gradually increasing control is performed at the start of the molding operation. Further, the control for gradually increasing the cushion amount is a simple control in which the forward stroke of the screw in the primary injection process is gradually shortened, so that it can be easily and reliably realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 4 relate to an in-line screw type injection molding machine according to an embodiment of the present invention (hereinafter referred to as the present embodiment). This embodiment is an injection for molding a disk substrate for DVD as a molded product. FIG. 1 is an example of an application to a molding machine, and FIG. 1 is a principal front sectional view showing a configuration of mainly an injection system of the injection molding machine of the present embodiment.

  In FIG. 1, 1 is an injection unit base board disposed on a main frame member (not shown), 2 is a headstock fixed on the injection unit base board 1, and 3 is an injection unit base board 1 in the same manner. The holding plate fixed on the top 4 is a heating cylinder whose rear end is fixed to the headstock 2, 5 is a nozzle attached to the tip of the heating cylinder 4, and 6 is wound around the outer periphery of the heating cylinder 4. The mounted band heater, 7 is a screw arranged so as to be able to rotate and move forward and backward in the heating cylinder 4, and 8 is a guide bar bridged between the head stock 2 and the holding plate 3. 9 is a linear motion block that is inserted and guided by the guide bar 8 and can be moved forward and backward, and 10 is rotatably held by the linear motion block 9 and a screw holding rotation in which the rear end portion of the screw 7 is fixed. , 11 is a driven pulley fixed to the screw holding rotary body 10, 12 is a measuring servo motor (for screw rotation driving) mounted on the linear motion block 9, and 13 is an output shaft of the measuring servo motor 12. It is a drive pulley that is fixed and transmits the rotation of the measuring servo motor 12 to the driven pulley 11 via a timing belt (not shown).

  Reference numeral 14 denotes a ball screw mechanism having a screw shaft and a nut body screwed to the screw shaft. Reference numeral 15 denotes a screw shaft (ball screw mechanism) of the ball screw mechanism 14 rotatably held by the holding plate 3 via a bearing. 14 is a nut body of the ball screw mechanism 14 that is screwed to the screw shaft 15 and linearly moves by the rotation of the screw shaft 15 (linear motion portion of the ball screw mechanism 14), 17 is a nut body 16 A load cell block 18 disposed in a manner sandwiched between the linear motion block 9 and integrally connecting the nut body 16 and the linear motion block 9 is a driven pulley fixed to the end of the screw shaft 15. An injection (screw linear drive) servomotor 20 mounted on the holding plate 3 is fixed to the output shaft of the injection servomotor 19 and is injected via a timing belt (not shown). 9 rotate in a driven pulley to transmit to the driven pulley 18.

  Reference numeral 21 denotes a fixed die plate on which the fixed side mold 22 is mounted, and reference numeral 23 denotes a movable die plate on which the movable side mold 24 is mounted, which can be moved back and forth. ) Or mold opening, and when the mold clamping is completed, the cavity 25 is formed by the fixed mold 22 and the movable mold 24. During the continuous automatic molding operation for automatically molding the disk substrate, the tip of the nozzle 5 is pressed near the resin inlet of the fixed mold 22 by a nozzle touch / back mechanism (not shown) and its drive source. To maintain.

  In the configuration shown in FIG. 1, at the time of the metering process, the metering servo motor 12 is rotationally driven by a command from the system controller 31 to be described later, whereby the driven pulley 11 rotates via the drive pulley 13 and a timing belt (not shown). When driven, the screw holding rotator 10 integrated with the driven pulley 11 rotates, and the screw 7 integrated with the screw holding rotator 10 rotates in a predetermined direction. By the rotation of the screw 7, the resin material supplied to the rear end side of the screw 7 is transferred forward by the screw feeding action of the screw 7 while being kneaded and plasticized, and the molten resin is stored on the front end side of the screw 7. Accordingly, the screw 7 moves backward. At this time, the injection servo motor 19 is driven and controlled by pressure feedback control in accordance with a command from the system controller 31 described later, whereby the rotation of the injection servo motor 19 is controlled by the drive pulley 20, a timing belt (not shown), It is transmitted to the screw shaft 15 of the ball screw mechanism 14 via the driven pulley 18, and the rotational motion is converted into a linear motion by the ball screw mechanism 14, and the nut body 16, load cell block 17, linear motion block 9, screw holding of the ball screw mechanism 14. The screw 7 moves backward while the pressure (back pressure) applied to the screw 7 is controlled via the rotating body 10. Then, when one shot of molten resin is stored on the tip side of the screw 7 (when the screw 7 is retracted to a predetermined measurement completion position), the rotational drive of the screw 7 by the measuring servo motor 12 is stopped. .

  On the other hand, at the time of the primary injection process of the injection process, the servo motor 19 for injection is driven and controlled by speed feedback control according to a command from the system controller 31 to be described later, whereby the rotation of the servo motor 19 for injection is driven by the drive pulley. 20, it is transmitted to the screw shaft 15 of the ball screw mechanism 14 via a timing belt (not shown) and the driven pulley 18, and the screw shaft 15 is rotationally driven. The rotation of the screw shaft 15 causes the nut body 16 of the ball screw mechanism 14 to rapidly move. And the linear motion block 9 is rapidly advanced through the load cell block 17, whereby the screw 7, which is a member that moves forward and backward integrally with the linear motion block 9, is rapidly advanced. 7 is rapidly injected and filled into the cavity 25 of the mold.

  Further, during the pressure holding process of the injection process subsequent to the primary injection process, the injection servo motor 19 is driven and controlled by pressure feedback control according to a command from the system controller 31 described later. The rotation is transmitted to the screw shaft 15 of the ball screw mechanism 14 via the driving pulley 20, a timing belt (not shown), and the driven pulley 18, and the rotational motion is converted into a linear motion by the ball screw mechanism 14, and the nut body of the ball screw mechanism 14. 16, the pressure (holding pressure) applied to the screw 7 is controlled via the load cell block 17, the linear motion block 9, and the screw holding rotating body 10, and the resin remaining in the nozzle 5 from the screw 7 (referred to as cushion amount) The holding pressure is applied to the resin in the mold through the resin).

  As described above, the present embodiment is an application example to an injection molding machine that molds a disk substrate for DVD, and one molding cycle is as short as 2.0 seconds, and is thin. As a result of the rapid solidification of the molded product, the weight of the disk substrate, that is, the thickness of the disk substrate correlated with the weight is substantially determined in the primary injection process. The effect on the weight of the disk substrate is virtually negligible.

  FIG. 2 is a block diagram showing a simplified configuration of the control system of the injection molding machine according to the present embodiment. In FIG. 2, 31 is a system controller that controls the entire machine (injection molding machine), 32 is an input device for an operator to perform various input operations, and 33 is an image of various display modes for the operator. 34 is a sensor group including a number of sensors (position sensor, speed sensor, pressure sensor, rotation amount detection sensor, temperature sensor, etc.) disposed in each part of the machine, and 35 is a machine. This is a driver group consisting of a number of drivers (motor drivers, heater drivers, etc.) for driving and controlling actuators (such as the motors 12, 19 and mold opening / closing system motors) and heaters arranged in the respective parts. The display device 33 is a display device with a touch panel, and a part of the input device 32 is configured by a touch panel.

  In the system controller 31, 41 is a general control unit, 42 is an operation condition setting storage unit, 43 is a holding pressure switching position variable condition storage unit, 44 is a measured value storage unit, 45 is an operation process control unit, and 46 is a display. It is a control unit.

  The overall control unit 41 monitors and grasps the state of each unit in the system controller 31 and controls each unit in the system controller 31.

  In the operation condition setting storage unit 42, various operation control conditions input using the input device 32 or input from a removable storage medium (not shown) connected to the system controller 31 are stored in a rewritable manner. ing. The operation control conditions stored in the operation condition setting storage unit 42 include a metering process, a mold closing (clamping) process, an injection (primary injection and pressure holding) process, a cooling process, an eject advance process, and a molded product removal robot. The operation control conditions of each process such as the disk substrate take-out process and the eject retraction process, the temperature control conditions of the heating cylinder 4 and the mold, and the like. The holding pressure switching position (that is, a value indicating the screw advance stroke in the primary injection process) stored in the operation condition setting storage unit 42 has passed a predetermined number of shots since the start of the continuous automatic molding operation. And it becomes a suitable value when the temperature control of the heating cylinder 4 is in a stable state.

  In the holding pressure switching position variable condition storage unit 43, when the continuous automatic molding operation is started, the holding condition set and stored in the operation condition setting storage unit 42 from the start of operation until the predetermined number of shots elapses is stored. The calculation conditions for how to use the pressure switching position data variably are stored in a rewritable manner.

  In the measurement value storage unit 44, measurement information (position information, speed information, pressure information, rotation angle information, rotation speed information, temperature information, etc.) of each part of the machine is captured and stored in real time by the sensor group 34 or the like. .

  Based on the operation control program for each process prepared in advance and the set value of the operation condition for each process stored in the operation condition setting storage unit 42, the operation process control unit 45 is a state confirmation information and measurement value storage unit. The driver group 35 is driven and controlled while referring to the measurement information in 43 and its own timing information, and the operation of each process is executed. In addition, the operation process control unit 45 performs each molding cycle according to the variable conditions of the holding pressure switching position stored in the holding pressure switching position variable condition storage unit 43 until the predetermined number of shots has elapsed from the start of operation. The holding pressure switching position (that is, the screw advance stroke in the primary injection process) is changed to change the cushion amount for each molding cycle.

  Based on various display processing programs prepared in advance and fixed display data, the display control unit 46 refers to the contents of the operating condition setting storage unit 42 and the measured value storage unit 44 as necessary, and performs various types of processing. A display mode image is generated and displayed on the display device 33.

  FIG. 3 is a diagram showing a transition of the holding pressure switching position at the start of the continuous automatic molding operation in the injection molding machine of the present embodiment. In the example shown in FIG. 3, the first 10 shots from the start of the continuous automatic molding operation are discarded and the 11th shot is represented as the first shot. In this example, the holding pressure switching position as one of the operation control conditions of the injection process stored in the operation condition setting storage unit 42 is 3.00 mm.

  The operation process control unit 45 of the system controller 31 executes the injection process by using the operation control conditions of the injection process stored in the operation condition setting storage unit 42 for the first 10 cycles from the start of the continuous automatic molding operation. The overall control unit 41 of the system controller 31 handles the first 10 shots of the 10 cycles as a discard shot. The reason for this is that the initial 10 shots cannot be formed into a molded product due to resin purging and the like.

  When the first 10 cycles have elapsed, the operation process control unit 45 of the system controller 31 refers to the content of the holding pressure switching position variable condition storage unit 43 and holds the 11th molding cycle (first shot in FIG. 3). The injection is performed with the pressure switching position set to 2.65 mm. From the 12th molding cycle (second shot in FIG. 3) to the 20th molding cycle (10th shot in FIG. 3), the holding pressure switching position according to the first characteristic line 51. Is gradually increased. Here, the smaller the numerical value of the holding pressure switching position, the larger the screw advance stroke in the primary injection process and the smaller the cushion amount, so the 11 molding cycles (first shot in FIG. 3) to 20 molding cycles (10 in FIG. 3). The amount of cushion gradually decreases until the first shot). Further, the operation process control unit 45 refers to the content of the holding pressure switching position variable condition storage unit 43 from the 21 molding cycle (11th shot in FIG. 3) to the 50 molding cycle (40th shot in FIG. 3). Then, the holding pressure switching position is gradually increased according to the second characteristic line 52. Further, the operation process control unit 45 refers to the content of the holding pressure switching position variable condition storage unit 43 from the 51 molding cycle (41st shot in FIG. 3) to the 110 molding cycle (100th shot in FIG. 3). Then, the holding pressure switching position is gradually increased according to the third characteristic line 53, and the holding pressure switching position is set to 3.00 mm in the 110 molding cycle (100th shot in FIG. 3). Then, after the holding pressure switching position reaches 3.00 mm, the operation process control unit 45 stops the control for changing the holding pressure switching position.

  Note that the inclination decreases in the order of the first characteristic line 51 → the second characteristic line 52 → the third characteristic line 53. This is because if the holding pressure switching position is not variably controlled, the weight reduction is large at the early stage of the start of the continuous automatic molding operation as shown in FIG. This is because the degree of weight reduction tends to be gradually eliminated as the cycle proceeds, so that the weight reduction is appropriately corrected accordingly.

  The round plot in FIG. 4 shows that the first 10 shots from the start of continuous automatic molding operation are discarded and the holding pressure switching position from the 11th shot to the 110th shot is changed as shown by the characteristic line in FIG. In this case, data obtained by sampling the weight of the disk substrate from the 11th shot to the 210th shot is shown, and in FIG. 4, the 11th shot data is used as the 1st shot data. The square plot in FIG. 4 shows the disk substrate from the 11th shot to the 210th shot when the initial 10 shots are discarded from the start of the continuous automatic molding operation and the holding pressure switching position is fixed at 3.00 mm. FIG. 4 shows the data of the 11th shot as the data of the 1st shot.

  As is clear from FIG. 4, by performing control to gradually increase the cushion amount at the start of the continuous automatic molding operation as in this embodiment, the weight of the disk substrate is stabilized from the initial stage of the continuous automatic molding operation, It can be seen that the thickness of the disk substrate correlated with the weight of the disk substrate is also stable. Therefore, it is possible to reduce as many waste shots as possible when the molding operation is started up, and it is possible to obtain a good disk substrate from the early stage of the start of the continuous automatic molding operation. Further, the control for gradually increasing the cushion amount is a simple control in which the holding pressure switching position is gradually increased (the advance stroke of the screw in the primary injection process is gradually shortened), so that the realization thereof is easy and reliable. Become.

  In the above-described embodiment, the control is performed so that the cushion amount gradually increases for each shot after a predetermined number of shots has elapsed after the continuous automatic molding operation is started and a plurality of discarded shots are performed. However, during the period from the start of the continuous automatic molding operation until the predetermined number of shots has elapsed, control may be performed so that the cushion amount gradually increases for each shot. The same effects as those of the embodiment can be obtained.

It is a principal part cutting front view which mainly shows the structure of the injection system of the injection molding machine which concerns on one Embodiment of this invention. It is a block diagram which simplifies and shows the structure of the control system of the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the transition characteristic of the holding pressure switching position according to the number of shots in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the number of shots by the injection molding machine which concerns on one Embodiment of this invention, and the weight of a disc substrate, and the relationship between the number of shots by the conventional injection molding machine, and the weight of a disc substrate. . It is explanatory drawing which shows the relationship between the weight of a disc substrate, and the board thickness of a disc substrate. It is explanatory drawing which shows the relationship between the temperature of a heating cylinder specific site | part according to the number of shots, and the weight of a disc board | substrate by the conventional injection molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection unit base board 2 Headstock 3 Holding plate 4 Heating cylinder 5 Nozzle 6 Band heater 7 Screw 8 Guide bar 9 Linear motion block 10 Screw holding rotary body 11 Driven pulley 12 Measuring servo motor 13 Drive pulley 14 Ball screw mechanism 15 Screw shaft Reference Signs List 16 Nut body 17 Load cell block 18 Driven pulley 19 Injection servo motor 20 Drive pulley 21 Fixed die plate 22 Fixed die 23 Moveable die plate 24 Moveable die 25 Cavity 31 System controller 32 Input device 33 Display device 34 Sensor group 35 Driver group 41 Overall control unit 42 Operation condition setting storage unit 43 Holding pressure switching position variable condition storage unit 44 Measurement value storage unit 45 Operation process control unit 46 Display control unit 51 First characteristic line 52 Second characteristic line 53 3 characteristic line

Claims (3)

In the inline screw type injection molding machine,
The screw injection start position is the same until the predetermined number of shots has elapsed since the start of continuous automatic molding operation and multiple discarded shots have been performed, or until the predetermined number of shots has elapsed since the start of continuous automatic molding operation. However, an injection molding machine comprising a controller that controls to change the forward stroke of the screw in the primary injection process so that the cushion amount gradually increases with each shot. The injection molding machine according to claim 1,
An injection molding machine characterized in that the controller increases the degree of increase in the cushion amount just after the start of operation and decreases it before the predetermined number of shots. A molding control method for an inline screw type injection molding machine,
The screw injection start position is the same until the predetermined number of shots has elapsed since the start of continuous automatic molding operation and multiple discarded shots have been performed, or until the predetermined number of shots has elapsed since the start of continuous automatic molding operation. However, the molding control method is characterized in that the forward stroke of the screw in the primary injection process is changed so that the cushion amount gradually increases for each shot.

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